import { DisposableSymbols } from '@whatwg-node/disposablestack';
import { MaybePromise } from '@whatwg-node/promise-helpers';

type TopicDataMap = {
    [topic: string]: any;
};
type PubSubListener<Data extends TopicDataMap, Topic extends keyof Data> = (data: Data[Topic]) => void;
interface PubSub<M extends TopicDataMap = TopicDataMap> {
    /**
     * Publish {@link data} for a {@link topic}.
     * @returns `void` or a `Promise` that resolves when the data has been successfully published
     */
    publish<Topic extends keyof M>(topic: Topic, data: M[Topic]): MaybePromise<void>;
    /**
     * A distinct list of all topics that are currently subscribed to.
     * Can be a promise to accomodate distributed systems where subscribers exist on other
     * locations and we need to know about all of them.
     */
    subscribedTopics(): MaybePromise<Iterable<keyof M>>;
    /**
     * Subscribe and listen to a {@link topic} receiving its data.
     *
     * If the {@link listener} is provided, it will be called whenever data is emitted for the {@link topic},
     *
     * @returns an unsubscribe function or a `Promise<unsubscribe function>` that resolves when the subscription is successfully established. the unsubscribe function returns `void` or a `Promise` that resolves on successful unsubscribe and subscription cleanup
     *
     * If the {@link listener} is not provided,
     *
     * @returns an `AsyncIterable` that yields data for the given {@link topic}
     */
    subscribe<Topic extends keyof M>(topic: Topic): AsyncIterable<M[Topic]>;
    subscribe<Topic extends keyof M>(topic: Topic, listener: PubSubListener<M, Topic>): MaybePromise<() => MaybePromise<void>>;
    /**
     * Closes active subscriptions and disposes of all resources. Publishing and subscribing after disposal
     * is not possible and will throw an error if attempted.
     */
    dispose(): MaybePromise<void>;
    /** @see {@link dispose} */
    [DisposableSymbols.asyncDispose](): Promise<void>;
}

export type { PubSub as P, TopicDataMap as T, PubSubListener as a };